Secret boxers:
In Open Style, fight until you are champion to access a Jack-In-The-Box boxer. Defend the championship title five times to access Snake.

In Peek-A-Boo, fight until you are champion to access Kiki and Mimi. Defend the championship title five times to access Edward King (the promoter).

In Peek-A-Boo, fight until you are champion to access Roboxer. Defend the championship title five times to access Carrie (the girl that carries the round cards).

Tip:
When you start carreer keep fighting Bill Price and you will always win. He is so weak and you should get an offer from the boxer at 18th rank. I was undefeated and challenged the champ after 9 matches.